1. Field of the Invention
The present invention relates generally to medical devices and methods, and more particularly to a system and method for endoluminal grafting of blood vessels or other tubular, main anatomic conduits which have furcations or side branches extending there from.
2. Related Art
Endoluminal grafting is a relatively noninvasive method for placing a tubular graft within the lumen of a native, main anatomic conduit, such as a blood vessel. In certain cardiovascular applications of conventional or prior art techniques for endoluminal grafting, an endovascular graft may be implanted in the aneurismal segment of a blood vessel to form a prosthetic blood flow conduit through the aneurysm, and to effectively isolate the weakened portion of the blood vessel wall from hemodynamic forces and pressures of the flowing blood.
The prior art has included numerous endovascular grafts of varying design. In general, these endovascular grafts typically comprise a tube made of a pliable material such as PTFE, polyester, woven Dacron®, etc., in combination with a graft anchoring component (e.g., a stent, a frame, hooks, a series of wire rings, clips, staple, etc.) that operates to hold the grafts in its intended position within the blood vessel.
An example of a commonly used endovascular primary stent graft is the AneuRx stent graft sold by Medtronic. A sleeve may be used at the end of the graft if the graft itself is not sufficiently long. With or without the sleeve, a conventional endovascular stent graft requires the neck (the area of the vessel between the branches and the aneurysm) to be of sufficient size to permit attachment of the graft. A conventional endovascular stent graft cannot be used if the neck is too short (this problem is described in some detail in U.S. Pat. No. 6,428,565 to Wisselink, in the paragraph bridging columns 2 and 3).
Endovascular grafting is a clinically-acceptablealternative to traditional surgery in patients who suffer from aneurysms of the aorta. Indeed, many patients who are diagnosed with aortic aneurysms are relatively high-risk patients and may be classed as poor-risk for traditional surgery. If allowed to remain untreated, the aneurysm will surely dissect or rupture, causing a catastrophic event leading to significant risk of death to the patient. The traditional surgery in itself incurs significant risk of morbidity and mortality to the patient, due to its inherently extensive nature, which includes excessive blood loss, intra-operative heart attacks, and organ system ischaemias due to the cross-clamping of the aorta, which is an inherent part of the procedure. Thus, endovascular grafting offers a potential means of repair of aortic aneurysm without the risks and potential complication of traditional surgery. At the present time, endoluminal grafting can be performed in patients with aneurysms isolated to the infra-renal position or at the juxta-renal position with great benefit to the high-risk patients, but is not extendable to a large population of patients that suffer with aneurismal disease of the aorta that involves its major branches.
Depending on which region of the aorta is/are involved, the aneurysm may extend into areas of bifurcation (i.e., the inferior end of the aorta where it bifurcates into the iliac arteries) or segments of the aorta from which smaller branches extend. In this regard, aortic aneurysms can be classified into three basic types and five sub-types on the basis of the regions of the aneurismal involvement, as follows:                A. Thoracic Aortic Aneurysms:                    1. Aneurysms involving the ascending aorta            2. Aneurysms involving the aortic arch and branches that emanate therefrom (i.e., subclavian artery, common carotid artery, innominate artery)                        B. Thoracoabdominal Aortic Aneurysms: Aneurysms involving the descending thoracic aorta and arteries that emanate from it (i.e., thoracic intercostals arteries) and/or the supra-renal abdominal aorta and branch arteries that emanate therefrom (i.e., renal, superior mesenteric, celiac, and/or the intercostals arteries).        C. Abdominal Aortic Aneurysm:                    1. Aneurysms involving the para-renal aorta and the branches that emanate therefrom (i.e., the renal arteries).            2. Aneurysms involving the infrarenal aorta with or without iliac involvement.                        
Unfortunately, not all the patients diagnosed with aortic aneurysm are presently considered to be candidates for endovascular grafting. This is largely due to the fact that most of the endovascular grafting systems are not designed for use in regions of the aorta from which side branches (i.e., carotids, innominate, subclavian, intercostals, superior mesenteric, celiac, renal) extend. In fact, most endovascular grafting systems have been in the treatment of infra-renal aneurysms, with or without the involvement of the iliac arteries. There are numerous examples in the prior art of endovascular grafting method and systems useable to treat such infra-renal aneurysms, with or without iliac artery involvement.
Patent Application Publication No. 2002/0103495 and U.S. Pat. No. 6,352,543 (Cole) disclose methods and devices for forming an anastomosis between hollow bodies using magnetic force to couple anastomotic securing components 78, 80 and create a fluid-tight connection between the lumens of the hollow bodies. End-to-side, side-to-side, and end-to-end anastomoses can be created without using suture or any other type of mechanical fasteners, although any such attachment means may be used in conjunction with the magnetic attachment The securing components have magnetic, ferromagnetic, or electromagnetic properties and may include one or more materials, for example, magnetic and nonmagnetic materials arranged in a laminated structure. As shown in FIG. 9A, the securing component 78 includes two members, 78A, 78B disposed on opposite surfaces of a wall of one of the hollow bodies. FIGS. 19A-19C show an embodiment in which one of the securing components has a flange-type construction. The system of anastomotic securing components may be used in many different applications including the treatment of cardiovascular disease, peripheral vascular disease, forming AV shunts for dialysis patients, etc., and may be sized and configured for forming an anastomosis to a specific hollow body, for example, a coronary artery or the aorta.
Patent Application Publication No. 2002/0143347 (Cole et al.) discloses methods and devices using magnetic force to form an anastomosis between hollow bodies. End-to-side, side-to-side, and end-to-end anastomoses can be created without using sutures or any other type of mechanical fasteners, although such attachment means may be used in practicing some aspects of the invention. Magnetic anastomotic components may be attached to the exterior of a vessel, e.g., by adhesive, without extending into the vessel lumen. Various magnetic component configurations are provided and may have different characteristics, for example, the ability to match the vessel curvature or to frictionally engage the vessel. FIG. 5B shows sutures S used to attach the component 16 to a vessel V, although it is stated that any suitable mechanical fastener may be used, e.g., clips, stents, barbs, hooks, wires, etc. FIG. 8B shows a magnetic anastomotic component 50 having an opening 52 and attachment structure 54 to facilitate securing the component to a vessel (not shown). As above, the structure 54 may be used alone or in combination with other means for securing the component to the vessel. In the illustrated embodiment, the attachment structure 54 is affixed to the component 50 to define a plurality of openings 56 which may be use to receive sutures, clips, clamps, pins, barbs, or other securing or fastening means.
Patent Application Publication No. 2001/0041902 (Lepulu et al.) discloses anastomotic methods and devices for placing a target vessel in fluid communication with a source of blood. FIGS. 11 and 12 show an embodiment utilizing magnets to secure the target vessel wall. In FIG. 11, a first securing component 90, preferably having a rectangular shape with rounded ends, is formed of magnetic material (or provided with magnetic material), as is a second securing component 92. The poles of the magnets are arranged to attract the components 90, 92 to one another and capture the tissue of the target vessel wall. FIG. 12 shows another embodiment wherein a first securing component 94 is carried by a conduit body 96, which is provided with a magnetic collar 98. A second securing component 100 has a magnetic collar 102, the poles of these magnets being arranged to repel the collars and force the components 94, 100 together.
U.S. Pat. Nos. 5,989,276 and 6,293,955 and Patent Application Publications Nos. 2003/0014061, 2003/0014062, 2003/0014063, 2001/0051809, and 2002/0052637 (Houser et al.) disclose a bypass graft incorporating fixation mechanisms at its opposite ends, for securing these ends to different locations along a blood vessel, or alternatively to different locations wherein one of the locations is a different vessel or an organ defining a cavity. Mechanical fixation features such as collets or grommets can be employed, enhanced by delivery of an electrical current sufficient to heat surrounding tissue to form a thermal bond. A graft deployment system includes a tissue dilator and a needle for perforating tissue, mounted coaxially within the dilator. Intraluminal systems further include a catheter for containing the dilator. To further assist positioning, magnets may be incorporated into the dilator near its distal tip, as indicated at 206 for a dilator 208 shown in FIG. 25. Such magnets may be formed of ferrite materials, or alternatively may be formed by winding conductive coils around the dilator to form electromagnets when current is supplied. The dilator magnets are used in conjunction with a guide wire 209 advanced beyond a stenosed lesion 210 within a vessel 212. The guide wire is formed of metal, and to further enhance magnetic attraction may incorporate a magnet 214 of opposite polarity to the dilator magnet. Magnetic positioning is stated to facilitate placing bypass grafts through tortuous vessels or over long distances beyond the lesion.
Houser et al. also disclose tissue dilators of deployment systems for graft fixation. Magnets may be incorporated into the dilator near its distal tip, as indicated at 206 for a dilator 208 shown in FIG. 25. Such magnets may be formed of ferrite materials, or alternatively may be formed by winding conductive coils around the dilator to form electromagnets when current is supplied. The dilator magnets are used in conjunction with a guide wire 209 advanced beyond a stenosed lesion 210 within a vessel 212. The guide wire is formed of metal, and to further enhance magnetic attraction may incorporate a magnet 214 of opposite polarity to the dilator magnet. Magnetic positioning is stated to facilitate placing bypass grafts through tortuous vessels or over long distances beyond the lesion.
U.S. Pat. Nos. 6,074,416 and 6,451,048 and Patent Application Publication No. 2002/0151913 (Berg et al.) disclose connector structures 34 for attaching elongated flexible tubular grafts to the body organ tubing of a patient. The connector structures are formed from nitinol wire.
U.S. Pat. No. 6,068,654 (Berg et al.) discloses a two-piece graft connector having a tubular band section with its proximal end configured to attach to a tubular graft and retention loops extending from its distal end, and a tubular anchor structure configured to be placed in the patient's tubular body tissue structure. The retention loops 26 can be made of nitinol wire. In one embodiment (see FIG. 1), the proximal end of the tubular band section is attached to a tubular graft. The retention loops extend from the distal end of the tubular band section of the connector, through an aperture in the side wall of a patient's tubular body tissue structure, and the tubular anchor structure is placed in the patient's tubular body tissue structure, within the retention loops. In another embodiment (see FIG. 9), retention loops 26 are replaced by relatively thicker retention fingers 70, which do not form loops, but instead form arcs, extending partially around the circumference of tubular body structure 11.
Methods for graft placement are disclosed in Patent Application Publications Nos. 2002/0143383 (Parodi) and 2002/0072790 (McGuckin, Jr. et al.) and U.S. Pat. No. 6,428,565 (Wisselink). Wisselink also describes the problems associated with using a conventional endovascular stent graft when the neck is too short (see the paragraph bridging columns 2 and 3).
With reference to FIGS. 15a-21, U.S. Pat. No. 6,068,637 (Popov et al.) discloses a method and devices for performing end-to-side anastomoses between the severed end of a first hollow organ and the side-wall of a second hollow organ utilizing a modified cutter catheter which is introduced into the first hollow organ in combination with a receiver catheter which is introduced into the second hollow organ. The distal end of the receiver catheter includes a receiver cavity and a selectively activatable magnetic material. The magnetic material is selected so that it will interact with a magnetically susceptible material disposed in the distal end of the modified cutter catheter when the modified cutter catheter is disposed in proximity to the proposed site for anastomosis whereby the severed end of the first hollow organ is matingly engaged with the sidewall of the second hollow organ. Thereafter, the severed end of the first hollow organ can be attached in sealing engagement with the side-wall utilizing clips, a biocompatible glue, or other suitable methods. The cutter is then activated to remove a portion of the side-wall of the second hollow organ, thereby creating an opening within the region of securement and establishing the anastomosis. In the preferred embodiment, the portion of the sidewall of the second hollow organ is engaged in the receiver cavity by the attractive force between the magnetically susceptible material and the magnetic material. The magnetically susceptible material is then released from the modified cutter catheter and withdrawn along with the portion of the sidewall removed by the cutter when the receiver catheter is withdrawn from the second hollow organ.
Most, if not all, of the endovascular grafts that have been designed for use in treating infra-renal aneurysms require that a proximal neck of adequate length exists inferior to the renal arteries, in order to provide a region where the superior end of the graft may be securely anchored so that blood flow to the renal arteries is not restricted. The deployment of an endovascular graft within the regions of the aorta from which the branch anatomic conduits emanate presents an additional technical challenge, because in those cases, the endovascular graft must be designed such that it can be inserted, aligned, and deployed with discrete maintenance of blood flow to the side branch anatomic conduits by means of additional branch grafts that arise from the newly-constructed endoaortic graft. This should be done in a manner that maintains sufficient blood flow to the branch anatomic conduit and yet exclude the aneurismal segment of the aorta from the haemodynamic consequences.
U.S. Pat. No. 5,425,765 (Tifenbrun et al.) discloses an endovascular graft that has one or more openings or fenestrations formed at specific locations, to allow blood to flow from the aorta into one or more of the branch arteries. However, such fenestrations do not form discrete connections with the branch arteries through which blood flows into the branch anatomic conduits. As a result, the area surrounding the fenestrations is prone to leakage of blood around the fenestrations, which might lead to migration of the graft as well as exposing that segment of aorta to the systemic blood pressure and other systemic hemodynamic effects. This defeats the entire concept of treatment of aneurismal disease, as the aortic wall is not entirely excluded after placement of the endoluminal graft. The migration of the endoluminal graft that might occur due to leakage around the fenestration might also compromise the blood flow to the branch anatomic conduit.
U.S. Pat. No. 6,428,565 (Wisselink et al.) discloses an endovascular graft that forms connections with the branch anatomic conduit with separate conduits. However, the technique and methods disclosed by Wisselink et al. have inherent deficiencies in more than one area. Wisselink et al. use conventional x-ray imaging techniques to introduce the grafts into the human body, but do not describe the delivery system and the technique of delivery such that it would make the procedure safer and most efficient. The use of conventional radiological methods to position a stent, graft, or prostheses is routine, but in this instance, the landing zone is very limited. Thus, in conjunction with fluoroscopy, an additional technique is required to align the endoaortic graft with the branch anatomic conduit and position the branch graft in such a manner that once completed, a conduit is created that supplies the branch anatomic conduit with unhampered blood flow. Wisselink et al.'s method for coupling of the branch graft to the aortic graft is prone to dislodgement thus prone to leakage of blood around the prosthesis. This will also promote graft migration. Post-implant migration and leakage may lead to obstruction of blood flow to the branch anatomic conduits.
U.S. Pat. No. 6,352,543 (Cole et al.) discloses a method of forming anastomosis between two hollow bodies, and the use of magnetic force as a coupling force to form a fluid tight junction. Cole et al.'s method in all its embodiments uses magnetic material as an anastomotic securing force and thus forms the actual fluid tight connections. However, this technique causes a rigid connection between two hollow organs that may lead to potential problems due to their fixed nature, and in the event of anastomotic narrowing are not amenable to interventional techniques in correcting the problems. Cole et al.'s method uses magnetic force as a method of attachment and refers to it as the means of anastomosis.
Thus, in view of the above-discussed limitations and shortcomings, there remains a need in the art for development of new endovascular grafting systems and methods which (a) may be useable for endovascular grafting in regions of the aorta where branch anatomic conduits (e.g., subclavian, innominate, carotid, intercostals, celiac, mesenteric, renals and iliac arteries) extend, and/or (b) may enable more aortic aneurysms patients to be candidates for endovascular repair, and/or (c) may advance the state of the art of endovascular grafting to improve patient outcomes or lessen complications.
It is to the solution of these and other problems that the present invention is directed.